$\dfrac{3}{12} - \dfrac{1}{6} = {?}$
Answer: $ = {\dfrac{3 \times 1}{12 \times 1}} - {\dfrac{1 \times 2}{6 \times 2}} $ $ = {\dfrac{3}{12}} - {\dfrac{2}{12}} $ $ = \dfrac{{3} - {2}}{12} $ $ = \dfrac{1}{12}$